From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Anton Blanchard <anton@samba.org>,
Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
Ingo Molnar <mingo@elte.hu>, Jens Axboe <jens.axboe@oracle.com>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Rusty Russell <rusty@rustcorp.com.au>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Milton Miller <miltonm@bga.com>, Nick Piggin <npiggin@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] smp_call_function_many SMP race
Date: Tue, 23 Mar 2010 08:33:59 -0700 [thread overview]
Message-ID: <20100323153359.GM2517@linux.vnet.ibm.com> (raw)
In-Reply-To: <1269347203.5279.1650.camel@twins>
On Tue, Mar 23, 2010 at 01:26:43PM +0100, Peter Zijlstra wrote:
> On Tue, 2010-03-23 at 22:15 +1100, Anton Blanchard wrote:
> >
> > It turns out commit c0f68c2fab4898bcc4671a8fb941f428856b4ad5 (generic-ipi:
> > cleanup for generic_smp_call_function_interrupt()) is at fault. It removes
> > locking from smp_call_function_many and in doing so creates a rather
> > complicated race.
>
> A rather simple question since my brain isn't quite ready processing the
> content here..
>
> Isn't reverting that one patch a simpler solution than adding all that
> extra logic? If not, then the above statement seems false and we had a
> bug even with that preempt_enable/disable() pair.
>
> Just wondering.. :-)
If I understand correctly, if you want to fix it by reverting patches,
you have to revert back to simple locking (up to and including
54fdade1c3332391948ec43530c02c4794a38172). And I believe that the poor
performance of simple locking was whole reason for the series of patches.
Thanx, Paul
next prev parent reply other threads:[~2010-03-23 15:34 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-23 11:15 [PATCH] smp_call_function_many SMP race Anton Blanchard
2010-03-23 12:26 ` Peter Zijlstra
2010-03-23 15:33 ` Paul E. McKenney [this message]
2010-03-23 15:49 ` Peter Zijlstra
2010-03-23 21:31 ` Anton Blanchard
2010-03-23 16:41 ` Paul E. McKenney
2010-05-03 14:24 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2011-01-12 4:07 Anton Blanchard
2011-01-17 18:17 ` Peter Zijlstra
2011-01-18 21:05 ` Milton Miller
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